JXCPC 1011

这是简单的比赛签到题，类似于A+B Problem 。

Class

Problem Description

Avin has two integers $a, b (1 \leq a, b \leq 1, 000)$.
Given $x = a + b$ and $y = a - b$, can you calculate $a * b$?

Input

The first line contains two integers $x, y$.

Output

Print the result of $a * b$.

Sample Input

4 2

Sample Output

3

program

/*
*@Author:   ChenShou
*@Language: C++
*/
#include<bits/stdc++.h>
#include<functional>
#include<algorithm>
#include<iostream>
#include<cstdlib>
#include<cstring>
#include<cstdio>
#include<string>
#include<vector> 
#include<bitset>
#include<queue>
#include<deque>
#include<stack>
#include<cmath>
#include<list>
#include<map>
#include<set>

//#define DEBUG
#define RI register int
#define endl "\n"

using namespace std;
typedef long long ll;
//typedef __int128 lll;
const int N=100000+10;
const int M=100000+10;
const int MOD=1e9+7;
const double PI = acos(-1.0);
const double EXP = 1E-9;
const int INF = 0x3f3f3f3f;

int main(){

#ifdef DEBUG
    freopen("input.in", "r", stdin);
    //freopen("output.out", "w", stdout);
#endif
    //ios::sync_with_stdio(false);
    //cin.tie(0);
    //cout.tie(0);
    //scanf("%d",&t);
    //while(t--){
    //}
    ll x , y ;
    while(scanf("%lld %lld",&x,&y)!=EOF)
    cout<<(x*x-y*y)/4<<endl;
#ifdef DEBUG
    printf("Time cost : %lf s\n",(double)clock()/CLOCKS_PER_SEC);
#endif
    //cout << "Hello world!" << endl;
	return 0;
}